准噶尔盆地玛北地区三叠系百口泉组储层成岩作用及孔隙演化

Diagenesis and Pore Evolution of Triassic Baikouquan Formation in Mabei Region,Junggar Basin

以岩心观察和铸体薄片鉴定为基础,结合扫描电镜以及测井和录井等资料综合分析,对准噶尔盆地玛北地区三叠系百口泉组储层的岩石学及物性特征、成岩作用及孔隙演化规律进行了研究。研究结果显示:研究区砂砾岩储层成分成熟度和结构成熟度均较低,孔隙类型主要为粒间溶蚀孔,储层物性较差,属于低孔低渗储层;储层埋藏较深,成岩作用复杂,成岩演化阶段主要处于晚成岩B期,经历了压实作用、胶结作用、溶蚀作用等多种成岩作用。压实作用为造成储层原生孔隙减少的主要因素,储层原始孔隙因压实作用损失平均达19.5%;其次为胶结作用,造成孔隙度减少平均为7.2%;而易溶组分发生的溶蚀作用形成的次生孔隙则有效地改善了储层的物性。研究区溶蚀作用增加的孔隙度约为5.2%,溶蚀作用形成的次生孔隙发育带成为研究区低孔低渗背景下发育的优质储层富集带。

Base on core observation and casting thin section, combining with the analysis on scanning-electron microscope, as well as the comprehensive logging and mud logging data, the characteristics of reservoir sandstone, physical property, diagenesis, and pore evolution of the Triassic Baikouquan Formation in Mabel region,Junggar basin were studied. The results show that the study area of sand-conglomerate reservoir is low in composition, structure maturity, porosity, and permeability; and the pore types are mainly intergranular dissolution pores. The reservoir buried deeply in the study area, and the Triassic Baikouquan Formation in Mabel region is mainly formed in the late diagenetic stage B period, experienced complex diagenesis, including mainly compaction, cementation, dissolution. The compaction is the main factor that caused the original porosity reduction,By 19. 5%, and cementation decreased the porosity for about 7.2 % ; while dissolution is constructive to the reservoir property as it can generate a great quantity of secondary porosity. Dissolutionin increased the porosity for about 5.2 %. The secondary porosity zone formed by dissolution has become a high-quality reservoir zone with the background of low porosity and permeability in the study area.